Precipitation gauges are well known in the art and there are a plethora of various devices which are employed for the collection of precipitation. As an example, manual measurements of snow have conventionally been taken using the Nipher gauge. This requires an observer to measure the depth of snow in the gauge and to melt the snow to determine the water equivalent of the precipitation.
In terms of automated sensors, there are two broad categories for these instruments, namely: heated and unheated arrangements. Heated arrangements have a heated surface that funnels the melted precipitation to a heated measuring device. These are typically retrofitted rain gauges that are used for liquid rain fall. Unheated solid precipitation gauges, frequently weigh the precipitation collected in a bucket or measure the pressure increase from precipitation collected in a drum. Various potentionmetric arrangements are known in the art as well.
The main drawback of the manual measurement arrangement is that they require an observer. Heated automated gauges are not recommended for sub-zero winter conditions because they have been attributed to effecting sublimation and evaporation and therefore are inaccurate in the sense that they underestimate precipitation. They also require a power source for the heat which limits them to sites with a hydro connection and therefore limits the utility in terms of portability applications.
In addition to the above, conventional arrangements require shielding to help improve the capture of, for example, blowing snow.
Turning to the automated systems, automated weighing or mass oriented gauges typically include chart recording gauges that have the chart replaced with a transducer to electrically output the signal measured by the spring weighing mechanism. These gauges are not well designed for winter precipitation because they have a deep "throat" that the snow has to pass to get to the weighing bucket to which the snow can adhere. The resolution of these gauges is typically not greater than 0.2 mm and the level of uncertainty is substantially higher. To compound the drawbacks of these systems, the cost of the arrangements is very significant and can approach $7,000.00 or greater.
In terms of specific prior art, U.S. Pat. No. 3,216,246, issued Nov. 9, 1965 to Blondeau et al., provides an atmospheric fall-out collector having a dual functioning collection surface. The apparatus is designed to collect dry fall-out, for example, dust and other particulate material by making use of an adhesive surface. Wet or liquid precipitation is collected by making use of a generally hemispherical deflector member which deflects the liquid downwardly into a funnel arrangement and further into a collection reservoir. Although a useful arrangement, the Blondeau et al. device would be limited in terms of its utility for collecting frozen precipitation.
Quinteros, in U.S. Pat. No. 2,570,710, issued Oct. 9, 1951, discloses a pluviometer having a receptacle to which is swingably mounted a collection reservoir in the form of a hollow semi-sphere. The semi-sphere additionally provides two wind vanes to direct the open semi-sphere into contact with the precipitation to be collected. The precipitation is then deposited into a receptacle to which the semi-sphere is rotatably mounted. Similar to the above-mentioned apparatus in the Blondeau disclosure, this apparatus would appear to be limited to the collection of liquid precipitation.
U.S. Pat. No. 3,958,457, issued May 25, 1976, to Mink, provides an electronically operated tipping bucket rain gauge where a rotary bucket wheel is positioned beneath and in fluid communication with a water column of collected rain. When the column exceeds a given height as determined by an electronic probe, the bucket is actuated and a predetermined water is removed from the bottom of the water column. Clearly, this apparatus would not be particularly useful in conditions where frozen precipitation is to be collected.
Govoni et al., in U.S. Pat. No. 5,291,779, issued Mar. 8, 1994, provide a snow collector wherein there is provided a receptacle adapted to receive a flexible liner for the collection of the precipitation. The Govoni et al. apparatus would appear to be limited to collection up to the point of the maximum volume of the flexible liner and subsequent to this, it would appear that collection would not be possible.
Additional prior art which is generally relevant to the precipitation collection art includes U.S. Pat. No. 2,954,690, issued Oct. 4, 1960, to Dickenson and U.S. Pat. No. 2,997,875, issued Aug. 29, 1961, to Moore and U.S. Pat. No. 2,497,795, issued Feb. 14, 1950, to Cappleman, Jr.
In view of what the prior art has previously proposed for precipitation collection, it is clear that there exists a need for an improved arrangement which is not limited to a specific volume collection and which can accurately provide a representative collection sample of any type of precipitation in any conditions without the inaccuracies typically associated with the prior art.